A press fit fastener, especially a wheel stud, is known from German Patent No. 43 18 494 C1. The known press fit fastener includes a shank, a head being located at one end of the shank and a press fit portion being located at the shank. The press fit portion includes a multiple helical profile. As any other thread, the helical profile also includes a beginning portion and an end portion. The helical profile includes a plurality of convolutions having a respective angle of inclination, the so-called helix angle. With the known press fit fastener, the desired press fit connection may be securely attained if the corresponding bore in the component has been produced with comparatively high quality, meaning with a comparatively small tolerance. In the case of bores of this kind, such a small tolerance is to be understood as a tolerance approximately in the region of IT 7 or less according to the ISO tolerances. Such exact manufacture of the diameter of the bore requires additional treatment after initial drilling. For example, such treatment may include grinding or rubbing to improve the surface quality. This second additional processing step increases the production cost for the manufacture of the component and consequently for the elements of the press fit connection to be attained. The known press fit fastener is always used in combination with a bore located in the component which has been manufactured by at least two production steps.
Theoretically, it would also be possible not to use a second finishing process step, or the bore could have a comparatively great tolerance due to other reasons. Such a bore then has a tolerance in a region of approximately IT 10 to IT 12. This means that the difference of the values of the inner diameter of the greatest bore within the tolerance zone and the smallest bore within the tolerance zone is comparatively great. In case the known press fit fastener was introduced into such a bore in the component having a comparatively great inner diameter, the overlap and the friction resulting therefrom would not be sufficient to ensure the desired press fit. There would be the danger of the press fit fastener being unintentionally detached from the bore. In the other case, if the known press fit fastener was introduced into a bore having a comparatively small inner diameter, there would necessarily be strong elastic and plastic deformations of the press fit portion of the press fit fastener as well as of the bore of the component. As a result, there would be undesired tension in the component and in the press fit fastener. The press fit fastener and/or the component including the corresponding bore could then not be reused after first detachment of the press fit connection. Consequently, the bore and the fastener could not be reused to realize another press fit connection.
A wheel stud including an axial knurl is known from the leaflet of KAMAX “Wheel studs. For passenger cars and commercial vehicles. KAMAX Connecting the world” (edition 2001). The illustrated knurled wheel stud may be used for realizing a press fit connection with a corresponding bore being located in a hub and being produced with a comparatively great tolerance. The axial knurled stud does not include a helical profile in the press fit portion. Instead, it includes a knurled press fit portion including knurls which extend in an axial direction. This means that the press fit portion includes a majority of adjacent parallel ribs and channels. In case such a known axial knurled stud is pressed into a bore having a comparatively small inner diameter being located in a hub being made of a comparatively soft material, there will be strong elastic and plastic deformations in the region of the inner surface of the bore of the component. Due to the strong axial direction of the ribs, the inner surface of the bore will also be plastically deformed to attain a knurled design. When the known axial knurled stud is introduced into a comparatively small bore of a hub being made of a comparatively hard material, there will be shearing effects in the region of the tips of the ribs of the knurl. In both hereinabove explained cases, the substantial elastic and plastic deformations, are the reason why the known stud and/or the component cannot be reused. This means that it is not possible to dismount the stud from the bore and to later introduce this stud into this bore, to introduce this stud into another bore, or to introduce another stud into this bore.
Another fastener for connecting two components under pre-tension is known from U.S. Pat. No. 3,418,012. The known fastener includes a tapered swaging portion with channels and ribs substantially extending in an axial direction. In contrast to a thread or to a helical profile, the channels and the ribs are either arranged exactly axially, meaning with an angle of inclination of 90°, or with an angle of inclination being slightly below 90°. The fastener is introduced into two aligned bores being located in two components being arranged one above the other. For this purpose, the bores have been commonly produced in the two components such that the diameter of the cylindrical bore is approximately between 1/1000 inch to 12/1000 inch smaller than the maximum diameter of the shank of the fastener being directly located below the head. The fastener is introduced into the bore by a rotational movement. This rotational movement results in elastic and plastic deformation of the formerly cylindrical bore. Due to the cone-like shape of the shank of the fastener, the bore is deformed such that it also attains a conical design.
Press fit fasteners including a shank, a head being located at one end of the shank and a press fit portion including knurls are known from British Patent No. 891,807 and U.S. Pat. No. 3,252,495. The knurl element consists of spaced apart, parallel knurled portions continuously extending about the axis of the fastener. The knurl portions include knurl elements substantially extending in the direction of the axis of the fastener. Preferably, the knurl elements are inclined by an angle of approximately 10° with respect to the screw axis to ensure rotation of the press fit fastener when introducing the fastener into a corresponding bore.